An onomatopoeia most likely first used by The Notorious B.I.G. in his 1994 debut album (Ready to Die) song, Gimme The Loot. It's used to describe the sound of a gunshot and/or the sound(s) heard in a fight such as, Boom, Pow, Blam, etc.

The Notorious B.I.G.: Man, niggas come through I'm taking high school rings too. Bitches get stripped down for they earrings and bangles and when I rock her and drop her I'm taking her door knockers, and if she's resistant Blakka! Blakka! Blakka!